PROJECT SUMMARY/ABSTRACT Magnesium (Mg2+) is an essential element found in all cells and is intimately involved in a myriad of biochemical processes and physiological functions. Improper regulation of Mg2+ in humans has been linked to diseases such as diabetes, hypertension, and immunodeficiency. Therefore, monitoring Mg2+ levels could aid in diagnosis and treatment of these disease states; however, current technologies for measurement of Mg2+ are not amenable to rapid, point-of-care analysis, and are limited by a need for extensive sample preparation or a lack of selectivity for Mg2+ over other cations. This proposal describes a hybrid carbon nanotube-molecularly imprinted polymer (CNT-MIP) chemiresistive sensor designed to selectively detect Mg2+. The proposed system consists of a CNT network modified with a functional enediyne that triggers the formation of a diradical upon binding Mg2+. In the presence of alkene- containing monomers, the diradical initiates a polymerization that propagates around the Mg2+-complexed template molecule. Removal of the Mg2+ template affords a polymer-coated CNT network with binding cavities that are expected to be highly selective for the recognition of Mg2+, and the binding event will be detected using conductometric measurements. Because the functional enediyne acts as both an initiator and an Mg2+-binding group, precise spatial control of the binding sites near the CNT network can be achieved while maintaining a direct connection from the binding site to the CNT. The MIP portion of the sensor is expected to provide the CNT network with structural robustness and resistance to deleterious bulk current leakage, which is normally problematic in aqueous CNT-based sensors.